1. Field of the Invention
This invention relates generally to swimming pool maintenance and, more specifically, to a system for automatically adjusting both the chlorine content and the pH level of the water in a swimming pool. The invention provides a safe system for continually adding small amounts of chlorine gas to the flow of water through the pool filtration system to disinfect the pool, and also to add an acidifying agent to the pool to maintain the pH at a comfortable level.
2. Description of the Prior Art
In the past, controlling the bacteria level and maintaining the chemical balance in a swimming pool have been ongoing problems. Control of bacterial growth in a swimming pool has generally been effected by adding chlorine to the pool water. While large swimming pools justified the installation of a bottled chlorine gas system, which allowed an operator to bleed gaseous chlorine into the pool water as required, the bulk and hardware expense of such a system precluded its use on anything less than a very large pool system.
Smaller swimming pools, including the common backyard-variety pool, typically relied upon the manual addition of chlorine compounds, in the form of pellets or granules, to control bacteria growth. The compounds were added to the pool water to adjust the chlorine content to a level which controlled the bacterial growth in the pool. The chlorine addition was carried out by dropping a fresh supply of chlorine compound directly into the pool water. The chlorine level rose substantially with the addition, causing wide variations in the concentration of the chlorine dissolved in the water and making the precise regulation of the chlorine level difficult, at best. Such an approach to control of bacterial growth was imprecise, due to both the intermittent nature of the addition of a fresh charge of chlorine-releasing compound, and to the substantially uncontrollable rate at which the chlorine compound dissolved. However, it established an effective control over the rate at which bacteria multiplied in the pool, provided that the person maintaining the pool monitor the chlorine level at frequent intervals to detect when chlorine addition was required.
Provision and control of the chlorine level with chlorine tablets or granules had a serious problem, however, in that such prepared chlorine compounds were expensive. It was not unusual to spend from $20.00 to $40.00 in a single month to maintain a safe chlorine level in a small domestic pool, with approximately a 30,000 gallon capacity.
Furthermore, normal use of a swimming pool tended to introduce an alkali content into the pool water. Both body-borne contaminants and solar input, to an outdoor pool, tended to increase the pH of the pool to an unacceptable level. To control the pH level in a pool, acid had to be added. Normally, dilute hydrochloric, or "muriatic", acid was added manually to adjust the pH level. Such a process was inconvenient, time-consuming and also made control of the pH level difficult.
Electrolytic chlorine generators were also known as a source for chlorine gas with which to disinfect a swimming pool. However, such electrolytic gas generators as were used in the past on swimming pools utilized a salt solution as an electrolyte. The salt was expensive, and subsequent to electrolysis left an alkaline residue. The residue was caustic and presented a disposal problem which had to be periodically addressed.
A need existed for an apparatus or method to automatically adjust the chlorine level in a swimming pool to control the growth of bacteria in the pool. A need further existed for a system to chlorinate a swimming pool, which system was reasonable in installation cost and was further low in operating cost. A need existed for a system to automatically adjust the pH level in a swimming pool by adding, on an ongoing basis, an acidifying agent to the pool at a controlled rate.
A need continued to exist for an electrolytic, chlorine gas-conditioning system for a swimming pool which did not require periodic removal of an alkaline residue.